I. Field of the Invention
The present invention relates generally to munitions and, more particularly, to a projectile for use with a tapered bore gun.
II. Description of Relevant Art
Guns having a tapered bore barrel have been used in combat since WWII and their popularity has waxed and waned since that time primarily because projectiles designed to be tired from these guns often exhibited compliant flanges that proved to have marginal structural integrity due to significant deformation while traversing the tapered section of the gun as well as unreliable aerodynamic stability due to the projectile's flanges inability to adequately engage with the rifling resulting in inconsistent gyroscopic stabilization. Modern tapered bore gun typically include a first constant diameter bore extending from the firing chamber of the bore to an intermediate point of the gun barrel and a smaller caliber bore extending a short distance from a front end of the barrel. A tapered bore section then connects the larger diameter first bore with the smaller diameter second bore. Alternatively, the tapered bore may extend continuously from the chamber to adjacent the muzzle. Rifling is present in the initial bore section of the tapered bore gun to impart spin to the projectile about its longitudinal axis. The spin acts to gyroscopically stabilize the projectile, improving its aerodynamic stability during flight.
When a projectile is fired from the tapered bore gun, the larger, initial caliber bore of the gun barrel provides for enhanced acceleration of the projectile during gun launch which results in a higher muzzle exit velocity compared to a constant diameter gun of the same caliber as the tapered gun's emergent caliber. The projectile is compressed radially inward by the tapered bore to a smaller diameter that is more aerodynamic due to its smaller frontal area and more streamlined geometry enabling the projectile to achieve greater velocities at extended ranges. However, as the projectile is radially compressed, it elongates due to the metallic projectile material being incompressible, i.e. the volume of the projectile is conserved, as it plastically deforms. However, the ability of a projectile to be gyroscopically stabilized decreases with increasing projectile length. Therefore, the radial compression of the projectile by the tapered bore must be such that it the emergent-geometry projectile is aerodynamically stable during flight.